Helicopter control is normally performed by a trained pilot, who operates the “collective,” “cyclic,” throttle and other flight controls to cause the helicopter to adopt particular attitude(s), and to cause the helicopter to fly in a particular direction, or to maintain a position and altitude (hover). It is not enough for a hovering control system to simply maintain the helicopter at a particular location, but it is also necessary to have a controlled attitude at that particular location. Otherwise, the helicopter might adopt an undesirable attitude, such as inverted. In order to hover at a particular location, an automatic system must link the helicopter flight controls with a sensor system which determines the location and attitude, and with a processor which determines the deviation of location and attitude from the desired location and attitude. Normally, such systems are degenerative feedback systems of some sort. U.S. Pat. No. 4,213,584, issued Jul. 22, 1980 in the name of Tefft et al. describes such a system using longitudinal and lateral accelerometers, together with a vertical gyro, for state sensing. Another such automatic control is described in U.S. Pat. No. 6,793,173, issued Sep. 24, 2004 in the name of Salesse-Layergne. FIG. 1 is a representation of the overall system of Salesse-Layergen. In FIG. 1, a helicopter system designated generally as 9 includes the helicopter 10 itself, and various system elements mounted on the helicopter 10. In FIG. 1, a sensor suite is illustrated as a block 12. The sensor suite 12v determines the various state parameters of the vehicle. A block 13 represents adjustment means or controls by which the pilot can select desired states. A set of actuators 14 which interact with the control axes of the helicopter 10 under the influence of commands from an automatic control device 16. The control device 16 receives sensor states and compares the sensor states with the desired settings of state, and issues such commands to the actuator 14 to cause the states of the helicopter 10 to tend toward the desired values.
Any helicopter automatic flight control system requires sensors responding to six degrees of freedom in order to operate. These six degrees of freedom are the position or location in three mutually orthogonal coordinates, together with roll, pitch, and yaw.
Improved or alternative sensors for three- or six-degree of freedom state determination are desired.